The Black Photo Spacer (BPS) technology is to integrate two processes of a BM (Black Matrix) and a PS (Photo Spacer) in a conventional liquid crystal display (LCD) into one process, and the black light shielding photosensitive resin is used to form three functional structures of different heights, which are the main photo spacer (Main PS), the sub photo spacer (Sub PS) and the black matrix from high to low.
FIG. 1 and FIG. 2 show structural diagrams of a conventional liquid crystal display manufactured by using BPS technology. By dicing the color resist layer 13′ of the gate line region (see the F′ region in FIG. 1), the main photo spacer 140′ and the sub photo spacer 141′ are both covered with black light shielding photosensitive resin and formed. In the areas for forming main spacer 140′ and the sub photo spacer 141′, the main pad 130′ and the sub pad 131′ of different heights are respectively formed. The final top height difference between the main photo spacer 140′ and the sub photo spacer 141′ is obtained by the leveling and filling effect after BPS coating.
The final height difference between the main photo spacer 140′ and the sub photo spacer 141′ will affect the safety range of the liquid crystal margin (LC Margin) in the cell process, thereby affecting the yield rate. In many existing applications, it comes to a problem that the height difference is too small; meanwhile, in the prior art, the top surface of the sub photo spacer 141′ is not sufficiently flat enough.